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TOPIC: UMIK-1 + ESI U24 XL - 2 ch measurement with REW

UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 4 weeks ago #39805

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Some of my customers in Finland have rejected UMIK-1 as measurement tool for loudspeaker design because it can't be used in 2 ch measurement with electrical reference signal. I have been solving this problem for a while and I think I got the solution figured out.

I have sold ESI U24 XL interface among UMIK-1 as simple sound card that offers analog outputs and both coaxial and optical digital outputs. It has very good connectivity in most cases. The interface has also the same connections in as out and ASIO-support for drivers.

I use Win10 myself and it is possible to connect multiple USB-interfaces with ASIO4ALL on Windows to REW. This makes it possible to connect the electrical loop cable on ESI's analog connection, set the loop output and input on REW to those and direct the main measurement signal to ESI's output while measuring input is UMIK-1.

There might be a problem that the digital delay on system varies when rebooting or restarting REW, but it seems like it is stable during one session which should be enough. I did some measurements today and they are behind the link. Here is a screenshot of impulse responses of different measurements on the same microphone position. The floor noise from my room varies a little. There is also a measurement where the microphone has been moved about 50 cm closer to the speaker. They seem to have the same timing.


Jussi Hoffrén @ aaninen.fi
Last Edit: 4 months 4 weeks ago by aaninen.
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 3 weeks ago #39808

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Interesting idea, but I don't understand the measurement. The timing reference should remove the delay due to the computer, so that the impulse peak represents acoustic delay time only. In your measurement, the impulse delay is 223 ms.
?
:)
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 3 weeks ago #39811

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Good point. The measurement (231 ms) includes delay from UMIK-1 and ASIO4ALL input drivers.

Distance between microphone and speaker was about 1,5 meters and 231 ms is about 76 meters (344 m/s). This is the problem, that the internal delay from UMIK-1 and input drivers varies on different sessions. It seems that the measurements are comparative when they are made during one session. I haven't tried yet different sessions, but this is what I have been told.

From ASIO4ALL settings I tapped the hardware buffers to be used. In case loudspeaker design is the use for the measurements , the internal delay among acoustic delay doesn't matter, because you only need to compare the impulse response and its timing between the drivers you are using and all the measurements have the same extra delay. Of course the impulse timing can be adjusted from the measurements and the extra delay can be removed.

This is just the only way to measure timing and phase accurate with UMIK-1 so that the data can be used on precise loudspeaker modeling for example with LspCAD or VituixCAD.

john.reekie wrote:
Interesting idea, but I don't understand the measurement. The timing reference should remove the delay due to the computer, so that the impulse peak represents acoustic delay time only. In your measurement, the impulse delay is 223 ms.
?
:)
Jussi Hoffrén @ aaninen.fi
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 3 weeks ago #39812

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Actually the extra delay is UMIK-1 internal delay - (minus) ESI U24 XL internal delay. Let me know, if that's not correct.
Jussi Hoffrén @ aaninen.fi
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 3 weeks ago #39817

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Different day and different delays. Though now the internal delays seem more correct.




Any way, this isn't a problem if you measure all you need during one session.
Jussi Hoffrén @ aaninen.fi
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 2 weeks ago #39970

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For all the ones interested on this, I can share new measurement data for REW.

aaninen.fi/media/2ch-measuring/


I booted and changed the USB-ports between three measurements. Seems like the inner delay varies depending on which USB-ports has been used. My laptop has three and I changed between two ports.

There is more information on the notes of the measurements.
Jussi Hoffrén @ aaninen.fi
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UMIK-1 + ESI U24 XL - 2 ch measurement with REW 4 months 5 days ago #40088

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Thanks much for sharing this method Jussi!

USB on any works asynchronously, so depending on when you're starting your measurement (and the state of the buffer), it will have varying delay. Hence the reason why REW introduced the timing reference since 5.15
www.minidsp.com/applications/auto-eq-wit...measuring-time-delay

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